1. Field of the Invention
The present invention relates to an apparatus achieving a high density, zero-height board-to-board interconnect, and, more particularly to an apparatus suited for optical and electrical interconnections.
2. Description of the Related Art
Modern electronic equipment widely employ electrical connectors. Often, electrical connectors are utilized for coupling printed circuit boards together. One typical use of a connector is for connecting main circuit boards, or mother boards to other circuit boards, or xe2x80x9cdaughter boards.xe2x80x9d
Typically, mother board connectors include a xe2x80x9ccard edgexe2x80x9d including housing with rows of conductive contacts within a slot for receiving a daughter board with contact pads. Mother board connectors typically include spring biased conductive contacts for maintaining electrical contact with the daughter board. Other types of contacts for mating mother boards to daughter boards include fork and blade contacts, and pin and receptacle contacts. Also known are flexible circuits for connecting points on a printed circuit board. Flexible circuits include conductive traces disposed on a flexible substrate with pressure mounted connectors for making contact between printed circuit boards.
When making connections between printed circuit boards, the considerations for determining the type of connector include the interconnection height, required signal density and the amount of mechanical float. Typically, connections between printed circuit boards occur in only a single axis due to the mating connectors""s requirement to be displaced during interconnection. When additional axes of connection are required, connectors must be made to float, flex or rotate. For example, a printed circuit board with two axes requiring connections typically must have one or both connectors with the ability to float, flex or rotate into position. The mechanical difficulties in the typical two axis connector results in a limited number of signals. Attempts at employing flexible circuits have proved disadvantageous due to the decreased signal density and decreased reliability of flexible circuits. Further, flexible circuits typically bend in only one dimension.
The problems of connecting in multiple dimensions is compounded for circuit board interconnections of optics modules to mother boards. More particularly, optics modules require both electrical and optical interconnections to be mated, but with different displacements and different axes. Typically, optical connectors require large displacements during the mating of the connectors and in a different axis than the electrical connectors. As a result, the prior art teaches a board-to-board electrical connector with a discrete connection height for the electrical connection in tandem with optical connectors on loose fiber xe2x80x9cpigtailsxe2x80x9d for optical connections. However the xe2x80x9cpigtailsxe2x80x9d for optical connections present problems of signal density and reliability. In typical board-to-board interconnections, the electrical connectors present problems with distance between the circuit boards in space-limited applications.
What is needed is a connection mechanism that allows electrical and optical connections to be made on a single module with zero height between the module and the mother board. Additionally, what is needed is a connection mechanism that allows multiple axis connections.
Accordingly, a method and circuit board assembly provide a zero interconnection height in a board-to-board interconnect while maintaining efficient space allocation for multiple axis connections by providing a floating connection in one plane thereby enabling a connection in another plane. More specifically, a method for interconnecting includes aligning a first circuit board having a first plurality of through-holes with a second circuit board having a second plurality of through-holes by matching the first plurality of through-holes with the second plurality of through-holes, the aligning providing an interconnection height of zero between the first circuit board and the second circuit board, aligning at least one pass-through socket with the aligned combination of the first circuit board and second circuit board, the at least one pass-through socket including pass-through socket through-holes, and inserting one or more pins disposed on a pin header through the at least one pass-through socket, the first circuit board and the second circuit board.
The method further includes floating one of the first circuit board and the second circuit board prior to inserting the pin header, the floating enabling the first circuit board to interconnect with the second circuit board with a connector aligned along an axis different from the pin header. In one embodiment the connector is an optical connector, and one of the first circuit board and the second circuit board is an OC-X transmit module, such as an OC-192 transmit module, disposed in a synchronous optical network (SONET) communication system.
A method for interconnecting a first circuit board in multiple axes of connection includes connecting the first circuit board to a second circuit board in a first axis, the connecting fixing the relative positions of the first circuit board and the second circuit board in one plane, aligning the first circuit board having a first plurality of through-holes with the second circuit board having a second plurality of through-holes by floating the first circuit board in another plane to match the first plurality of through-holes with the second plurality of through-holes, the aligning providing an interconnection height of zero between the first circuit board and the second circuit board, aligning at least one pass-through socket with the aligned combination of the first circuit board and second circuit board, the at least one pass-through socket including pass-through socket through-holes, and inserting one or more pins disposed on a pin header through the at least one pass-through socket, the first circuit board and the second circuit board.
Another embodiment of the present invention is directed to a circuit board assembly. The circuit board assembly includes a mother board having a first plurality of through-holes, a daughter board having a second plurality of through-holes, the daughter board disposed with zero interconnection height relative to the mother board, at least one pass-through socket coupled to the combination of the mother board and the daughter board, the at least one pass-through socket disposed on an exterior side of the combination of the mother board and the daughter board, and a pin header having one or more pins, the one more pins insertable through the at least one pass-through socket and the combination of the mother board and the daughter board via the first and second pluralities of through holes, the one or more pins making electrical contact to signal contacts disposed in the mother board and the daughter board when the one or more pins are inserted.
In one embodiment, electrical contact with the one or more pins is maintained by spring force of signal contacts in the through holes. In another embodiment, the daughter board is connected via a connector, the connection fixing the daughter board and the mother board in a first plane, the daughter board floating in a second plane prior to the insertion of the one or more pins through the at least one pass-through socket and the combination of the mother board and the daughter board. In another embodiment, the daughter board floats relative to the mother board prior to the insertion of the one or more pins of the pin header, the float enabling the daughter board to interconnect with the mother board with a connector, such as an optical connector, aligned along an axis different from the axis in the direction of the one or more pins of the pin header.